1 2 /* 3 * Copyright 2011 Google Inc. 4 * 5 * Use of this source code is governed by a BSD-style license that can be 6 * found in the LICENSE file. 7 */ 8 #include "SkUnitMappers.h" 9 10 SkDiscreteMapper::SkDiscreteMapper(int segments) { 11 if (segments < 2) { 12 fSegments = 0; 13 fScale = 0; 14 } else { 15 if (segments > 0xFFFF) { 16 segments = 0xFFFF; 17 } 18 fSegments = segments; 19 fScale = SK_Fract1 / (segments - 1); 20 } 21 } 22 23 uint16_t SkDiscreteMapper::mapUnit16(uint16_t input) { 24 SkFixed x = input * fSegments >> 16; 25 x = x * fScale >> 14; 26 x += x << 15 >> 31; // map 0x10000 to 0xFFFF 27 return SkToU16(x); 28 } 29 30 SkDiscreteMapper::SkDiscreteMapper(SkFlattenableReadBuffer& rb) 31 : SkUnitMapper(rb) { 32 fSegments = rb.readU32(); 33 fScale = rb.readU32(); 34 } 35 36 SkFlattenable::Factory SkDiscreteMapper::getFactory() { 37 return Create; 38 } 39 40 SkFlattenable* SkDiscreteMapper::Create(SkFlattenableReadBuffer& rb) { 41 return SkNEW_ARGS(SkDiscreteMapper, (rb)); 42 } 43 44 void SkDiscreteMapper::flatten(SkFlattenableWriteBuffer& wb) { 45 this->INHERITED::flatten(wb); 46 47 wb.write32(fSegments); 48 wb.write32(fScale); 49 } 50 51 /////////////////////////////////////////////////////////////////////////////// 52 53 uint16_t SkCosineMapper::mapUnit16(uint16_t input) 54 { 55 /* we want to call cosine(input * pi/2) treating input as [0...1) 56 however, the straight multitply would overflow 32bits since input is 57 16bits and pi/2 is 17bits, so we shift down our pi const before we mul 58 */ 59 SkFixed rads = (unsigned)(input * (SK_FixedPI >> 2)) >> 15; 60 SkFixed x = SkFixedCos(rads); 61 x += x << 15 >> 31; // map 0x10000 to 0xFFFF 62 return SkToU16(x); 63 } 64 65 SkCosineMapper::SkCosineMapper(SkFlattenableReadBuffer& rb) 66 : SkUnitMapper(rb) {} 67 68 SkFlattenable::Factory SkCosineMapper::getFactory() { 69 return Create; 70 } 71 72 SkFlattenable* SkCosineMapper::Create(SkFlattenableReadBuffer& rb) { 73 return SkNEW_ARGS(SkCosineMapper, (rb)); 74 } 75 76
